Multilayered ceramic board, method for fabricating the same, and electronic device using multilayered ceramic board

Abstract

A method for fabricating a multilayered ceramic board includes forming a green laminate, the green laminate including a plurality of green base layers containing a low-temperature sinterable ceramic material which is a ceramic powder and a glass component, and a binder; at least one green constraining layer disposed in contact with a principal surface of a specific green base layer, the green constraining layer containing an inorganic material powder which is not sintered at the sintering temperature of the low-temperature sinterable ceramic material; and wiring conductors; and firing the green laminate at the sintering temperature of the low-temperature sinterable ceramic material. The firing step includes a binder removal step and a sintering step for obtaining the sintered state of the low-temperature sinterable ceramic material in which the ceramic powder is densified while the glass component is fluidized. The rate of temperature increase from the binder removal step to the sintering step is set to be more than about ° C./minute.

What is claimed is:  
     
       1. A method for fabricating a multilayered ceramic board comprising: 
       providing a green laminate comprising a plurality of green base layers, at least one green constraining layer disposed in contact with a principal surface of at least one of the green base layers, and at least one wiring conductor disposed on a green base layer,  
       wherein the green base layer comprises a low-temperature sinterable ceramic material comprising a ceramic powder and a glass component which precipitates a crystalline substance selected from the group consisting of forsterite, akermanite and diopside during firing, and a binder; and the green constraining layer comprises an inorganic material powder which is not sintered at the sintering temperature of the low-temperature sinterable ceramic material; and  
       firing the green laminate at the sintering temperature for the low-temperature sinterable ceramic material,  
       wherein the firing comprises binder removal for removing the binder contained in the green base layers and sintering for obtaining the sintered state of the low-temperature sinterable ceramic material in which the ceramic powder is densified while the glass component is fluidized in the green base layer, and  
       wherein the rate of temperature increase from the binder removal to the sintering is more than about 20° C./minute so as to precipitate the forsterite, akermanite or diopside.  
     
     
       2. A method for fabricating a multilayered ceramic board according to  claim 1 , wherein green constraining layers are disposed on both ends in the lamination direction of the laminate, and the method further comprises removing the green constraining layers disposed on both ends in the lamination direction of the laminate after the firing. 
     
     
       3. A method for fabricating a multilayered ceramic board according to  claim 2 , further comprising mounting an electronic component on an external surface of the laminate after the firing. 
     
     
       4. A method for fabricating a multilayered ceramic board according to  claim 3 , wherein the rate of temperature increase from the binder removal to the sintering is at least 25°C./minute. 
     
     
       5. A method for fabricating a multilayered ceramic board according to  claim 4 , wherein the glass precipitates the crystalline substance before the firing is complete. 
     
     
       6. A method for fabricating a multilayered ceramic board according to  claim 5 , wherein the glass is a borosilicate glass. 
     
     
       7. A method for fabricating a multilayered ceramic board according to  claim 1 , wherein the rate of temperature increase from the binder removal to the sintering is at least 25° C./minute. 
     
     
       8. A method for fabricating a multilayered ceramic board according to  claim 1 , wherein the glass precipitates the crystalline substance before the firing is complete. 
     
     
       9. A method for fabricating a multilayered ceramic board according to  claim 8 , wherein glass is a borosilicate glass. 
     
     
       10. A method for fabricating a multilayered ceramic board according to  claim 1 , further comprising forming said green laminate.